Head to the center of the map where the key pedestals are and get on the gray ledge at the stairs. Follow this ledge counter-clockwise, jumping the gap, then going north to a megaarmor. (sector 31)

After using the switch at the southeast end of the map, the wall to the east will open up revealing arachnotrons and revenants. A switch is at the south end of this cage. Shoot it and head north, then through the passage at the east side to get a computer area map. (sector 628)

At the U-shaped bend in the center of the map, head into the blue liquid and find the green circle switch at the southwest end. Pressing it lowers the nearby lift, but also one to the northeast from where you are at. Quickly run out of the blue liquid and through the opening near the fence such that you are on the teal ledge. From there, you can collect the soul sphere. (sector 1020)